1. Field of the Invention
The present invention relates to a homogeneous charge compression ignition internal combustion engine.
2. Description of the Related Art
In recent years, a homogeneous charge compression ignition internal combustion engine that introduces a gaseous mixture which is obtained by previously mixing oxygen-containing gas and a fuel which is self-ignitable by compression into a combustion chamber and compresses it, and thereby, causes the fuel to self-ignite has been studied. In the above described homogeneous charge compression ignition internal combustion engine, a lean gaseous mixture is compressed at a high compression ratio and is caused to self-ignite, and therefore, all the fuel that is supplied to the combustion chamber burns substantially at the same time. As a result, according to the above described homogeneous charge compression ignition internal combustion engine, the fuel consumption per predetermined time can be reduced, and the quantity of air pollutant in exhaust gas can be reduced. However, in the above described homogeneous charge compression ignition internal combustion engine, pressure abruptly rises due to premature ignition at the time of a high-load operation, and therefore, there is the problem of occurrence of extremely large flame noise.
There has been conventionally known a homogeneous charge compression ignition internal combustion engine in which a low-octane fuel is supplied to an intake port and a high-octane fuel is supplied to the combustion chamber in order to prevent flame noise due to the above described premature ignition. According to the above described conventional art, the layer of a gaseous mixture including the low-octane fuel is formed in the vicinity of the peripheral wall of the inside of the combustion chamber, and the layer of a gaseous mixture including the high-octane fuel is formed at the central portion in the combustion chamber. When the above described gaseous mixture is compressed, the self-ignition combustion starts at the low-octane fuel, and therefore, the self-ignition combustion advances from the area in the vicinity of the peripheral wall of the inside of the above described combustion chamber to the central portion. As a result, the combustion period can be prolonged, and occurrence of flame noise can be reduced (see Japanese Patent Laid-Open No. 2000-179368).
However, the premixed mixture compression ignition internal combustion engine in which the low-octane fuel is supplied to the intake port and the high-octane fuel is supplied into the combustion chamber has the disadvantage of being incapable of obtaining the effect of reducing the occurrence of the above described flame noise depending on the kind of the high-octane fuel.